That's great! Congrats!
I don't know why I didn't see this thread before, but we're a lot alike. Our first, last, and only will be starting college in the fall, and so we're kind of aiming for 2024, after the last tuition payment! The thing is, we don't really have a target. Actually, FIREcalc and Fidelity's retirement planner say we could retire now, but we want to wait until our expenses are a bit lower (again, tuition), and maybe be able to upgrade our spending in retirement, particularly travel spending. We're flexible, though, so if it's the depths of a recession in mid-2024, we might work a bit more just so we aren't making withdrawals at the bottom of the market, but we probably could afford to do so if we wanted to...after all, most of it would stay in the market for decades.